Head position detector with optical slit pattern

ABSTRACT

A system and method that directs a transducer to a home position while taking into account whether a light source, used to detect light interruption is inoperative. The method for the system including a light source, a detector configured to receive signals from the light source, a transducer that reads signals from a magnetic tape and a plurality of structures coupled to the transducer and configured to pass in opposition to the detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to systems and methods for positioningand, more particularly, to systems and methods of positioning atransducer in a storage device such as a tape drive.

2. Description of Related Art

The 3584 LTO drive head is positioned based on the bottom position as areference position and moves to a specified position with a steppingmotor. The position of the head is unknown when the drive is switchedon. Then, the bottom position is sought while the head is moved. Thehead is sometimes moved out of the permissible range during the search,which may break the head mechanism.

Specifically, the conventional 3854 LTO drive has a light blockingshield, attached to the head, for detecting the bottom position and aphoto-interrupter attached to a case. The bottom position is based onthe border between the place where the photo-interrupter crosses thelight-blocking shield and the place where the photo-interrupter does notcross the light-blocking shield. If the photo-interrupter crosses thelight-blocking shield when the drive is switched on, the border can befound while the head is moved in the direction away from the bottom. Ifthe photo-interrupter does not cross the light-blocking shield, theborder can be found while the head is moved toward the bottom. If thesensor is unplugged, the drive is always in the same situation as whenthe photo-interrupter crosses the light-blocking shield. Accordingly, insuch a case, the method causes the head to keep moving in the directionaway from the bottom even over the range allowed for the head to move,which breaks the head mechanism.

The 3584 Gen4 drive has a mechanism for checking whether thephotoreceptor side of the photo-interrupter responds or not bycontrolling ON/OFF of the LED of the photo-interrupter for the purposeof checking the operation of the photo-interrupter. That can confirmthat the drive is plugged. If no response is detected, the mechanismcannot determine whether the drive is unplugged or the photo-interrupteris crossing the light-blocking shield. Then, the mechanism slightlymoves the head. If the head is already at the limit of the range allowedfor it to move, that movement breaks the head. (When the drive ispowered down, the head is usually placed at a place other than thebottom position to prevent that incident. Sometimes, however, the powerabruptly breaks when the head is at the bottom position.)

Mechanically, that incident can be prevented by removing the ditch ofscrews for the head not to move to out of the range. For that purpose,the length of the ditch to be removed needs to be wide enough for thesize of the head. This is not the best measure when the height of thedevice is limited.

The head may be physically stopped by an overshoot preventing piece(Japanese Unexamined Patent Application Publication No. 5-128701,Japanese Unexamined Patent Application Publication No. 10-334536.)

SUMMARY OF THE INVENTION

To address the problem above, there is a method for a system including alight source, a detector configured to receive signals from the lightsource, a transducer that reads signals from a tape, and a plurality ofstructures coupled to the transducer and configured to pass inopposition to the detector. The method comprises determining whether ornot a light signal is received by the detector; if the light signal isreceived, moving the transducer incrementally in a first direction; ifthe light signal is interrupted by moving the transducer within a firstdistance, the first distance corresponding to a distance betweenadjacent structures, moving the transducer in a direction opposite thefirst direction until the light signal has been continuously receivedacross more than the first distance; if the light signal is notinterrupted by moving the transducer within a first distance, continuingto move the incrementally in a first direction until the light signal isinterrupted; and if the first determining step determines that the lightsignal is not received, moving the transducer incrementally in adirection opposite the first direction, wherein the moving steps areeffected with a stepping motor.

BRIEF DESCRIPTION OF THE DRAWINGS

References are made to the following text taken in connection with theaccompanying drawings, in which:

FIG. 1 is a diagram showing an exemplary positioning system inaccordance with a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a plan view of the exemplary positioningsystem shown in FIG. 1.

FIG. 3 is a flowchart of processing performed by the first exemplarysystem.

The accompanying drawings which are incorporated in and which constitutea part of this specification, illustrate embodiments of the inventionand, together with the description, explain the principles of theinvention, and additional advantages thereof. Certain drawings are notnecessarily to scale, and certain features may be shown larger thanrelative actual size to facilitate a more clear description of thosefeatures. Throughout the drawings, corresponding elements are labeledwith corresponding reference numbers.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Exemplary Embodiment

FIGS. 1 shows a first exemplary system 1, including a transducer headbody 10, a stepping motor 20 for moving the head body 10, a photodetector 40 configured to receive light from the light source 45, and alight blocking shield 30. The light blocking shield 30 includesprojections 32, 34, 36, and 38 that define slits between theprojections.

FIG. 2 is a view taken along the line 2-2 and FIG. 1.

Stepping motor 20 moves head 10 between the case bottom 51 and the casetop 53. When transducer head 10 is near the case bottom 51, projections32, 34, 36, and 38 act to block the light received by photo detector 40.

In the description of the first exemplary embodiment, the width of theprojections is a, and the slit width between the projections is b.

The photo detector 40 is attached to the case bottom 51.

The distance the head 10 moves when 1 pulse is applied to the steppingmotor 2 is 1. The slits on the light-blocking shield 30 are such thatthe width of the light blocking area is a, the width of the aperture isb, and the number of light blocking areas is p. By taking account of theresolution of the photo-interrupter (approximately 0.2 mm), a=b=0.5 mm,p=4.

FIG. 3 shows a process, carried out by circuitry 100, that can determinethe bottom position without breaking the head 3 even if the device isunplugged. Circuitry 100 determines whether the photo detector 40 isreceiving the light. (step 1). If the light is received, it isdetermined that the device is plugged. Then, the operation proceeds tostep 2. If the light is blocked, it is determined that the device isunplugged or that the head is at the light-blocking area. Then, theoperation proceeds to step 5.

Move the head toward the bottom one by one.

When the light blocking area is found by moving the head by the distanceb or less, it is determined that the head is within the range oflight-blocking shields. Then, the operation proceeds to step 3.

When the light blocking area is not found by moving the head by thedistance b or less, it is determined that the head is upper than thebottom position. Then, the operation proceeds to step 4.

The head is moved upward. When the light has been serially received by aor more number of moving steps, it is determined that the head is justout from the range of light-blocking shields. Then, the head is returnedtoward the bottom by the distance a. Where the head is moved bya*p+b*(p−1) is the bottom position. Then, the operation proceeds to step9.

4. The head is moved until the light-blocking area is found at thebottom side. Where the head is moved by a*p+b*(p−1) from the position ofthe found light-blocking area is the bottom position. Then, theoperation proceeds to step 9.

5. Move the head upward one by one.

When an aperture is found by moving the head by the distance a or less,it is determined that the head is within the range of light-blockingshields. Then, the operation proceeds to step 3.

If the aperture is not found by moving the head by the distance a orless, it is determined that the device is unplugged. Then, the operationfinishes as an error.

9. It is determined that the head is at the bottom position and theoperation normally finishes.

In summary, system 1 includes a light source 45, a detector 40configured to receive signals from the light source, a head 10containing a transducer that reads signals from a tape, and a pluralityof projections 32, 34, 36, and 38 coupled to the transducer head 10 andconfigured to pass in opposition to the detector 40.

Circuitry 100 acts to determine if a light signal is received by thedetector 40. If the light signal is received, circuitry 100 sends asignal to motor 20, to move head 1 step toward the bottom. If the lightsignal is interrupted and the head has only been moved within the slitwidth b, circuitry 100 sends a signal to motor 20, to move the head 10toward the top until the light signal has been continuously receivedacross more than the distance b.

If the light signal is not interrupted by moving the transducer withinb, circuitry 100 continues to send signals to motor 20 to move head 10toward the bottom.

Second Exemplary Embodiment

The light-blocking shields are attached across the whole range of thehead.

The width of the aperture differs according to the place. Specifically,the width of the nth aperture is likebn=b1+d*n

Then, the current head position can be determined when the head is movedand the width of the nearest aperture is measured. By taking advantageof that, a difference of position due to loss of synchronization of thestepping motor can be corrected.

Throughout this Patent Application, certain processing may be depictedin serial, parallel, or other fashion, for ease of description. Actualhardware and software realizations, however, may be varied depending ondesired optimizations apparent to one of ordinary skill in the art.

In this Patent Application, the word circuitry encompasses dedicatedhardware, and/or programmable hardware, such as a central processingunit (CPU) or reconfigurable logic array, in combination withprogramming data, such as sequentially fetched CPU instructions orprogramming data for a reconfigurable array. Thus, circuitryencompasses, for example, a general-purpose electronic processorprogrammed with software, acting to carry out a described function.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific examples. The benefits,advantages, solutions to problems, and any element(s) that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot critical, required, or essential feature or element of any of theclaims.

Additional advantages and modifications will readily occur to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus, andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the spirit or the scopeof Applicants' general inventive concept. The invention is defined inthe following claims. In general, the words “first,” “second,” etc.,employed in the claims do not necessarily denote an order.

1. A method for a system including a light source, a detector configuredto receive signals from the light source, a transducer that readssignals from a magnetic tape, and a plurality of structures coupled tothe transducer and configured to pass in opposition to the detector, themethod comprising: determining whether or not a light signal is receivedby the detector; if the light signal is received, moving the transducerincrementally in a first direction; if the light signal is interruptedby moving the transducer within a first distance, the first distancecorresponding to a distance between adjacent structures, moving thetransducer in a direction opposite the first direction until the lightsignal has been continuously received across more than the firstdistance; if the light signal is not interrupted by moving thetransducer within a first distance, continuing to move the transducerincrementally in a first direction until the light signal isinterrupted; and if the first determining step determines that the lightsignal is not received, moving the transducer incrementally in adirection opposite the first direction, wherein the moving steps areeffected with a stepping motor.